1. Field of the Invention
The present invention relates to a reversible thermosensitive recording material capable of recording and erasing images repeatedly by utilizing its property that the transparency can be changed reversibly from a transparent state to an opaque state, and vice versa, depending upon the temperature thereof.
2. Discussion of Background
Recent years, some attention is paid to a reversible thermosensitive recording material capable of temporarily recording images thereon and erasing the same therefrom once such images are regarded as unnecessary. As the representative example of that kind of reversible thermosensitive recording material, there is conventionally known a reversible thermosensitive recording material in which an organic low-molecular-weight material such as a higher fatty acid is dispersed in a matrix resin such as vinyl chloride - vinyl acetate copolymer with a glass transition temperature (Tg) of as low as 50.degree. C. or more to less than 90.degree. C., as disclosed in Japanese Laid-Open Patent Applications 54-119377 and 55-154198.
In the case where only the heat energy is applied to the reversible thermosensitive recording material by using a heat-application roller or a heat-pen, with the pressure hardly applied thereto, in order to perform the recording and erasing operations, the durability of the recording material is not degraded even though the image formation and erasure is repeated. In contrast to this, when the heat and pressure are applied to the recording material at the same time by using a thermal head, the durability of the recording material is degraded during the repeated operations. This is because the matrix resin around the organic low-molecular-weight material particles in the recording layer is deformed and the organic low-molecular-weight material particles finely dispersed in the matrix resin ar gradually accumulated and the particles size thereof thus becomes bigger while the recording and erasing operations are repeated. As a result, the effect of scattering light is decreased, which lowers the whiteness degree of a white opaque portion in the recording layer Finally, the image contrast is disadvantageously lowered.